DUCKWORTH, Naftalin and Dalgarno

Fat Studies in Poultry 6. UTILIZATION OF FATS OF DIFFERENT MELTING POINTS* B. MARCH AND JACOB BIELY Poultry Nutrition Laboratory,^ The University of British Columbia, Vancouver, B. C, Canada DUCKWORTH, Naftalin and Dalgarno (1950) found that the difference in digestibility between low and high melting point fats reported for other animals exists also for the chick. Carver et al. (1955) and Sunde (1956) reported that hydrogenated fat is poorly utilized by the chick. The following experiments were conducted to study the nutritive value for the growing chick of fats of different satun. The effect of dietary fat level and of feeding surface active agents on the utilization of fat has been studied. Since there is little data available regarding the form in which fatty acids are excreted by the chick, the of split to unsplit fat excreted has been determined. EXPERIMENTAL Experiment 1. The composition of the ns used in the first experiment is shown in Table 1. The basal n included 12 percent cerelose. In the ns in which fat was included, cerelose was replaced on a pound for pound basis with 3, 6, 9 and 12 percent of either hydrogenated animal fat (HAF) or corn oil. The melting point of the HAF used in both experiments was approximately 55 C. Each n was fed to duplicate lots of 20 New Hampshire male chicks to 4 weeks of age. The average weights of the chicks at 4 weeks and the efficiency of feed utilization from 0-4 weeks are shown in Table 2. The fat content of the wet feces from * Carried out with the aid of a grant from the Canada National Research Council, f Contribution Number 93. (Received for publication July 9, 1956) 71 TABLE 1. Composition of basal diets Ingredient Ground yellow corn Ground wheat Cerelose Soybean oil meal (solvent extracted) Fish meal Meat meal Limestone Bonemeal Dehydrated cereal grass Dried butyl fermentation solubles Dried brewers' yeast Iodized salt ing oil 22S0A-300D Choline Chloride (25%) Manganese Sulphate Protein (calculated) the chicks was determined by the method of Hoagland and Snider (1943). The procedure was modified slightly in that fatty acids were extracted with 4-50 ml. portions of petroleum ether. The digestibility coefficients of the fat in the different ns are given in Table 2. The values represent an average of the results for three separate 24 hour periods on the 15th, 19th and 24th days of the experiment. The digestibility coefficients were not corrected for metabolic fat by itself but were calculated by correcting for the total fat (metabolic and undigested dietary) excreted by the chicks fed the basal n. Experiment 2. In Experiment 2, HAF was compared to beef tallow when fed in a chick n at a level of 12 percent. The effect of surface active agents on fat utilization was studied with per- Experiment 1 22.0 22.0 12.0 26.00 10.0 1.5 2.5 2.0 6gm. 25% Experiment 2 25.25 25.25 12.00 13.00 13.00 5.00 2.5 6gm. 25%

72 B. MARCH AND J. BIELY TABLE 2. Summary of data in Experiment 1 Fat supplement to basal diet None 3% HAF 6% HAF 9% HAF 12% HAF 3% corn oil 6% corn oil 9% corn oil 12% corn oil Average weight at 4 weeks 386 409* 392 378 364* 408* 418** 417** 402 1.99 2.05 1.96 1.97 2.06 2.00 1.81 1.79 1.90 Digestibility co- efficient of added fat 5 50.0 50.0 44.2 84.7 92.3 90.8 91.8 * Significantly different from average control weight at 5% level of significance. ** Significantly different from average control weight at 1% level of significance. MSD at 5% level 19. at 1% level 25. cent lecithin and 0.1 percent Santomerse- 80 respectively in the diets. The composition of the basal n is shown in Table 1. Each n was fed to 23-25 New Hampshire male chicks for 6 weeks. The average weights of the chicks and the efficiency of feed utilization for this period are summarized in Table 3. The procedure of Van de Kamer el al. (1949) was followed in this experiment for the determination of fat in feces. In this method fatty acids present in soap or as free fatty acids are determined separately from fatty acids present in neutral fat. Determinations were made on the feces collected on the 26th, 27th and 28th days of the experiments. The TABLE 4. Utilization of supplementary fat in Experiment 2 Supplement to basal diet Coefficient Coefficient of Digesti- of Digestibility 1 bility 2 % % Proportion of fat excreted as neutral fat % 12% HAF 73.5 23.1 34.S 12% HAF plus lecithin 68.3 23.3 41.3 12% HAF plus Santomerse-80 70.8 23.2 38.0 12% tallow 99.1 75.2 3.7 12% tallow plus lecithin 99.6 72.8 1.5 12% tallow plus Santomerse-80 99.9 72.5 0.3 1 Calculated from the neutral fat content of the feces. 2 Calculated from the total fatty acid content of the feces. digestibility coefficients of the two fats with and without surface active agents were calculated on the basis of the neutral fat excreted as well as on the basis of the total fatty acids excreted. The coefficients of digestibility of the fat supplements were calculated with correction for the fat excreted by the chicks fed the corresponding diet without added fat. When a surface active agent was included in the diet, the correction was made on the basis of the fat excreted by the chicks fed the basal diet supplemented with the surface active agent. The data regarding fat utilization are shown in Table 4. RESULTS AND DISCUSSION In Experiment 1 when 3, 6 and 9 percent of corn oil were added to the basal diet, growth of chicks was significantly faster. Twelve percent corn oil did not stimulate growth significantly. ef- TABLE 3. Average weights and feed efficiency of chicks at 6 weeks in Experiment 2 Supplement to basal diet none 12% HAF 12% beef tallow 716 639 703 None Lecithin Santomerse-80 (2.32) (2.55) (2.20) 695 632 683 (2.34) (2.54) (2.20) 658 666 653 (2.41) (2.40) (2.22) MSD at 5% level 55.

UTILIZATION or DIFFERENT FATS 73 ficiency was improved by the addition of 6 or 9 percent of corn oil to the diet and to a lesser extent, by 12 percent of corn oil. The addition of 3 percent ofhaf to the basal diet stimulated growth, but 6 and 9 percent of HAF were without effect. When added at the 12 percent level HAF depressed growth. HAF did not affect feed efficiency although it was itself poorly utilized. There was no effect on feed utilization with any of the levels of HAF used. HAF was only 50 percent utilized by the chick when fed at levels of 3, 6 or 9 percent and had an even lower coefficient of digestibility (44 percent) at the 12 percent level. The digestibility coefficient of the corn oil increased from approximately 85 percent when fed at the 3 percent level to 91-92 percent at dietary levels of 6, 9 and 12 percent. Since the melting point of the HAF was approximately 55 C, the poor digestibility was not unexpected. Duckworth, Naftalin and Dalgarno (1950) found that the difference in digestibility between low and high melting point fats reported for other animals exists also for the chick. Carver et al. (1955) reported that "neither hydrogenated tallow nor hydrogenated tallow fatty acids are efficiently utilized as fat supplements to broiler feed." Sunde (1956) concluded that the chick does not utilize saturated long chain fatty acids. The digestibility coefficient of the fat was influenced by the level at which it was fed. Corn oil was utilized equally well at levels of 6, 9 and 12 percent but not so completely when it comprised only 3 percent of the diet. HAF, on the other hand, was utilized to a similar extent whether fed at a level of 3, 6 or 9 percent of the diet, but was less well utilized when the level was raised to 12 percent. The drop in utilization of the HAF at this level was not reflected in the overall efficiency of feed utilization. These data do not agree with those on rats of Hoagland and Snider (1943) which indicated increased digestibilities for the least digestible fats when the intake was increased. They are in accord with those of Duckworth, Naftalin and Dalgarno (1950) however, which showed that the digestibility of mutton fat for the chick was depressed when the level was increased beyond 6 percent of the diet. In Experiment 2 the addition of 12 percent of HAF to the basal diet depressed the rate of growth of chicks fed the diet. efficiency, likewise, was adversely affected. The addition of 12 percent beef tallow, on the other hand, although not affecting growth rate, did improve the efficiency with which the n was utilized. Supplementation of the ns with percent of lecithin had no effect on either the rate of growth or the efficiency of feed utilization. Santomerse-80 depressed growth of chicks fed either the basal diet or the diet containing 12 percent tallow but had little or no effect on feed efficiency. The addition of Santomerse-80 to the diet containing 12 percent HAF did not depress growth and improved the efficiency with which the diet as a whole was utilized. On the basis of total fatty acids excreted, the digestibility of the hydrogenated fat in this experiment was only 23 percent. The discrepancy in the values obtained for the digestibility of the HAF between the two experiments was most probably due to the fact that a different sample of HAF was tested in each experiment and also that there were slight differences in the form in which calcium was supplied in the diets. Cheng, Morehouse and Deuel (1949) observed that the dietary levels of calcium and mag-

74 B. MARCH AND J. BIELY nesium had a marked effect on the digestibility of hydrogenated fats. Fat digestibility was not affected by the addition of a surface-active agent to the diet. Since the analytical procedure determined separately neutral fat and fatty acids, free and as soaps, it was possible to calculate the relative proportion of fat excreted in these forms. Following the same method of calculation as previously, the digestibility coefficients of HAF and tallow were also determined on the basis of the neutral fat excreted. From data shown in Table 3 it will be noted that when the digestibility coefficients were calculated in this way the data are more in accord with those in the literature. It is felt, however, that any method which does not take fecal soaps into considen in the calculation of digestibility coefficients of fats for the chicken cannot be considered as valid. Crockett and Deuel (1947), studying fat digestibility in the rat, made similar observations on the discrepancy between digestibility coefficients calculated with and without allowance in the calculations for the soaps excreted. In the case of the chicks fed tallow, only a small percentage (3.7 percent) of the fecal fat was in the form of neutral fat. The addition of lecithin to the diet reduced the percentage of tallow excreted as neutral fat to 1.5 percent. When Santomerse-80 was added to the diet with tallow, the amount of neutral fat excreted was scarcely more than was excreted by the chicks fed the basal diet with Santomerse-80 as supplement. When HAF was added as fat supplement, 34.5 percent of the fat in the feces was in the form of neutral fat. Presumably much of the neutral fat in the feces represented fat excreted unchanged from the form in which it was fed. Visual examination of the feces, in fact, showed small particles of the HAF which had not been completely broken down during passage through the digestive tract. The addition of lecithin to the diet containing HAF increased the proportion of neutral fat in the feces to 41.3 percent and Santomerse- 80 increased it to 38.0 percent. It has been indicated that, in the rat, the larger proportion of the fat excreted when saturated fats are fed is in the form of soap. Augur, Rollman and Deuel (1947) and Crockett and Deuel (1947) reported that, in rats, the highly saturated fats were not resistant to hydrolysis in the intestine but that the soaps formed from saturated fatty acids could not be absorbed. In the present experiment it will be seen that with both fats tested, the greater part of the excreted fat was in the form of soap and free fatty acid. In the feces from chicks fed HAF the proportion of split fat to unsplit fat was lower, however, than in the feces from chicks fed the less saturated tallow. This would indicate that in the chick the highly saturated fats are resistant to hydrolysis. The effect of the surface-active compounds was interesting when considered in terms of the findings of other investigators. Deuel (1955) states that it would be unlikely to expect an improvement in fat digestibility by the addition of a surface active agent to a diet containing a fat already possessing a high coefficient of digestibility. In the present experiment there was no indication that lecithin or Santomerse-80 had any beneficial effect on the utilization of either fat tested. On the basis of the relative proportions of neutral fat and fatty acids (free and as soap) excreted when percent lecithin was added to the diet supplemented with HAF, there was a shift towards a higher proportion of neutral fat in the feces. Santomerse-80 had a similar, though lesser, effect to lecithin. When the sur-

UTILIZATION OF DIFFERENT FATS 75 face-active agents were added to the diet supplemented with tallow, the action was in the reverse direction. The proportion of tallow excreted unhydrolyzed was very small in the case of the diet without surface-active agents and was reduced still further by either lecithin or Santomerse- 80. With the latter compound, the amount of neutral fat excreted on the diet with tallow added was reduced to such a degree that the total neutral fat present in the feces was no more than was excreted on the corresponding basal diet without added tallow. SUMMARY Corn oil, tallow and hydrogenated animal fat were studied as supplements to chick ns. Corn oil and tallow were well utilized by the chick. The coefficients of digestibility were not so high as those reported in the literature because fatty acids excreted in the form of soaps were taken into account in the present experiments. When fed at the 12 percent level the values obtained were approximately 90 percent for corn oil and 73 percent for tallow. Two samples of hydrogenated animal fat fed at the 12 percent level were utilized only to the extent of 44 and 23 percent respectively. Although there were differences in the distribution of fatty acids in the feces between split and intact fat when lecithin or Santomerse-80 was added to ns supplemented with either tallow or hydrogenated animal fat, there was no appreciable improvement in the digestibility of either fat. The greater part of fat excreted was in the form of soaps and free fatty acids. Chicks fed hydrogenated animal fat excreted a higher proportion of fat as triglyceride than did chicks fed the less saturated tallow. Highly saturated fats are evidently resistant to hydrolysis in the chick. Fecal soaps must be considered in any estimation of digestibility of fat by the chicken. ACKNOWLEDGMENT The authors are grateful to Gordon Young Ltd., Vancouver, B.C., for the tallow used in the experiments. REFERENCES Augur, V., H. S. Rollman and H. J. Deuel Jr., 1947. Effect of crude lecithin on the coefficient of digestibility and the rate of absorption of fat. J. Nutrition, 33:177-186. Carver, D. S., E. E. Rice, R. E. Gray and P. E. Mone, 1955. Utilization of fats of different melting points added to broiler feeds. Poultry Sci. 34: 544-546. Cheng, A. L. S., M. G. Morehouse and H. J. Deuel, Jr., 1949. Effect of the level of dietary calcium and magnesium on the digestibility of fatty acids, simple tri-glycerides and some natural and hydrogenated fats. J. Nutrition, 37: 237-250. Crockett, M. E., and H. J. Deuel Jr., 1947. A comparison of the coefficients of digestibility and the rate of absorption of several natural and artificial fats as influenced by melting point. J. Nutrition, 33:187-194. Deuel, H. J., Jr., 1955. The Lipids Vol. II: Biochemistry. Interscience Publ., Inc., New York. Duckworth, J., J. M. Naftalin and A. C. Dalgarno, 1950. Digestibility of linseed oil and mutton fat by chicks. J. Agric. Sci. 40:39-43. Hoagland, R., and G. G. Snider, 1943. Digestibility of some animal and vegetable fats. J. Nutrition, 25:295-302. Sunde, M. L., 1956. Effect of fats and fatty acids in chick ns. Poultry Sci. 35: 362-368. Van de Kamer, J. H., H. T. B. Huinink and H. A. Weyers, 1949. Rapid method for the determination of fat in feces. J. Biol. Chem. 177: 347-355. July 16-19. American Poultry Hatchery Feden Convention, Municipal Auditorium, Kansas City, Mo.